This document describes a method and apparatus for enhancing the charge collection function, using third generation telecommunication systems as an example.
The introduction of the third Generation Partnership Project (3GPP) and the third Generation Partnership Project 2 (3GPP2) harmonization effort known as IP (Internet Protocol) Multimedia Sub-system (IMS) has introduced new convergence network elements based on IP based signaling protocols and bearer connections. The goal is to create a harmonized wireless and wireline IP based control network for telecommunications. The IMS network nodes include the Proxy-Call Session Control Function (P-CSCF), Interrogating-CSCF (I-CSCF), Serving-CSCF (S-CSCF), Media Gateway Control Function (MGCF), the Breakout Gateway Control Function (BGCF), the Media Resource Function Controller (MRFC), and Application Servers (AS). In order to perform charging functions in the converged IMS network, each of the network elements have a defined interface to a new node called the Charging Collection Function (CCF). CCF, defined in 3GPP and 3GPP2 standards documents, is an off-line charging network node in the IMS network. CCF collects session charging information from IMS nodes, and constructs and formats Call Detail Records (CDRs). It provides intermediate data storage buffering and provides a mechanism to transfer charging information to the operator's billing system (BS).
For IMS, the CCF provides the mechanism to transfer charging information from the IMS nodes to the operator's chosen Billing System(s). The CCF is responsible for the collection of session charging information from the IMS nodes. The CCF may also act as an intermediate data storage device and therefore needs to support storage of CDRs for a specified period of time given a usage profile. Further, the CCF in 3GPP standards must create ASN.1 (Abstract Syntax Notation.1) base Charging Detail Records. These CDRs are transferred to the BS/BMD (Billing Mediation Device) nominally using FTP (File Transfer Protocol), but other protocols and transport methods are possible. The CCF can receive data from the IMS nodes in a near real-time mode. It should have enough storage to enable it to transmit the collected charging data to the BS in file mode. The CCF may support several transmission protocols towards the BS. One of the purposes for the CCF is to reduce the number of different interfaces between the BS and the IMS nodes sending charging data.
In the IMS system, on-line charging is conducted by an Online Charging Server (OCS). IMS nodes query OCS with charging information. OCS rates calls with a built-in rating engine and provides charging cost and generates CDRs. OCS can support both prepaid and postpaid modes.
3GPP and 3GPP2 are generalizing the aforementioned IMS charging architecture to the entire 3G network, which includes Circuit Switch and Packet Switch networks.
However, there are no standards (neither 3GPP nor 3GPP2) which support the charging and rating concept in CCF so that it cannot provide call cost in CDRs. All rating and billing information must be processed in a back office billing system. That limits the capability of IMS/CCF to postpaid and offline billing only.